The goals of this project are to study mechanisms underlying the developmental and homeostatic regulation of the gene expression, posttranslational modification, and secretion of neuropeptides with a focus on the magnocellular oxytocin and vasopressin neurons in the hypothalamus. Efforts are being made to develop in vitro (dissociated cell and slice explant cultures) and in vivo (transgenic mouse) model systems to study these issues. Preliminary results indicate that both types of model systems are close to being achieved. The approach is cell- biological and hence, the focus is on the activity and gene expression at the single cell level. For this purpose, immunocytochemical, in situ hybridization histochemical, and single cell mRNA techniques are utilized.